In the premises of a university, office or factory, a wired LAN using coaxial cables is often used in order to effect data transfer between information communication devices such as personal computers, work stations or facsimile devices. However, in the wired LAN, a large-scale work must be effected when the layout is changed after construction of the system. Thus, it has a problem that it is difficult to easily cope with a change in the layout after construction of the system. Therefore, recently, it is strongly required to provide a LAN using a radio circuit.
However, many factors must be taken into consideration in order to realize the radio LAN. For example, they include band-narrowing of the frequency band to be used, suppression of influences by the multipath and portabi-frequency selectivity fading, and achievement of portability of terminal devices as typical factors.
Conventionally, various studies have been made for the above various problems. However, effective solutions are not yet provided.